Intra-frame prediction and decoding methods and apparatuses for image signal

ABSTRACT

An intra-frame decoding method includes obtaining, from a video code stream, prediction mode information of a first signal component of a current block; determining a prediction mode of the first signal component of the current block from a prediction mode set of the first signal component of the current block according to the prediction mode information of the first signal component of the current block, where the prediction mode set of the first signal component of the current block includes at least one of a linear model above (LMA) mode and a linear model left (LML) mode; obtaining a predicted value of a first signal component sampling point of the current block; and obtaining a reconstructed value of the first signal component sampling point of the current block according to the predicted value of the first signal component sampling point of the current block.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/265,788, filed on Apr. 30, 2014, which is a continuation ofInternational Application No. PCT/CN2012/084079, filed on Nov. 5, 2012,which claims priority to Chinese Patent Application No. 201110347750.2,filed on Nov. 4, 2011. The aforementioned patent applications are herebyincorporated by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

TECHNICAL FIELD

The present disclosure relates to the field of communicationstechnologies, and in particular, to an intra-frame decoding method andapparatus for a signal component sampling point of an image block and aprediction method and apparatus for a signal component sampling point ofan image block.

BACKGROUND

Existing video image coding technologies include an intra-frame codingtechnology and an inter-frame coding technology. Intra-frame coding is atechnology of coding image content using only spatial correlation in acurrently coded image block. Inter-frame coding is a technology ofcoding a currently coded image block using time correlation between thecurrently coded image block and a coded image block.

To increase intra-frame coding efficiency for an image, an intra-frameprediction technology is first introduced in the H.264 Advanced VideoCoding (H.264/AVC) standard to remove spatial information redundancybetween a currently coded image block (hereinafter referred to as acurrent block) and an adjacent coded image block. The High EfficiencyVideo Coding (HEVC) solution is a new-generation video codingstandardization solution currently being studied by the InternationalOrganization for Standardization, which inherits and is extended fromthe intra-frame prediction coding technology in the H.264/AVC standard.A prediction mode set of a chrominance component of an image block mayinclude six optional prediction modes: a direct mode (DM) mode:prediction is performed using a prediction mode of a luminance componentof a current block as a prediction mode of a chrominance component ofthe current block; a linear method (LM) mode: a predicted value of achrominance component sampling point is calculated based on acorrelation model using a reconstructed value of a luminance componentsampling point, where a parameter of the correlation model is obtainedthrough calculation according to reconstructed values of luminancecomponent and chrominance component sampling points right above and onthe left of a current block; a direct current (DC) mode: an averagevalue of reconstructed values of adjacent chrominance component samplingpoints right above and on the left of a current block is used as apredicted value of a chrominance component sampling point of the currentblock; a planar mode: a predicted value of a chrominance componentsampling point of a current block is calculated based on an assumptionof spatial smooth linear variation of values of chrominance componentsampling points; a horizontal mode: a reconstructed value of achrominance component sampling point on the left side of a current blockis used as a predicted value of all chrominance component samplingpoints in a same row of the current block; and a vertical mode: areconstructed value of an adjacent chrominance component sampling pointright above a current block is used as a predicted value of allchrominance component sampling points in a same column of the currentblock.

Among the foregoing prediction modes, the DC mode, the vertical mode,the horizontal mode, and the planar mode have a same basic principle ascorresponding prediction modes in the H.264/AVC standard, but specificimplementation methods are different. The LM mode and the DM mode aretwo newly added prediction modes.

However, in the existing HEVC solution, a prediction mode set of achrominance component cannot adapt to the diversity of edge positions ofa current block, and in some cases, a prediction effect needs to beimproved.

SUMMARY

Embodiments of the present disclosure provide an intra-frame decodingmethod and apparatus for a signal component sampling point of an imageblock and a prediction method and apparatus for a signal componentsampling point of an image block, so as to improve the accuracy ofintra-frame prediction of a current block.

An embodiment of the present disclosure provides a prediction method fora signal component sampling point of an image block, which includescalculating, based on a correlation model, a predicted value of a firstsignal component sampling point of a current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point above the current block and a reconstructed value of asecond adjacent signal component sampling point above the current block.

An embodiment of the present disclosure further provides a predictionmethod for a signal component sampling point of an image block, whichincludes calculating, based on a correlation model, a predicted value ofa first signal component sampling point of a current block according toa reconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block and a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block.

An embodiment of the present disclosure further provides an intra-framedecoding method for a signal component sampling point of an image block,which includes obtaining, from a video code stream, prediction modeinformation of a first signal component of a current block; determininga prediction mode of the first signal component of the current blockfrom a prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block, where the prediction mode set of thefirst signal component of the current block includes at least one of alinear model above (LMA) mode and a linear model left (LML) mode;obtaining a predicted value of a first signal component sampling pointof the current block according to the prediction mode of the firstsignal component of the current block; and obtaining a reconstructedvalue of the first signal component sampling point of the current blockaccording to the predicted value of the first signal component samplingpoint of the current block.

An embodiment of the present disclosure further provides an intra-framedecoding method for a signal component sampling point of an image block,which includes obtaining, from a video code stream, prediction modeinformation of a first signal component of a current block; determininga prediction mode of the first signal component of the current blockfrom a prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block, where the prediction mode set of thefirst signal component includes a prediction mode based on a correlationmodel, and the prediction mode based on the correlation model isdetermined depending on a prediction mode of a second signal componentof the current block; obtaining a predicted value of a first signalcomponent sampling point of the current block according to theprediction mode of the first signal component of the current block; andobtaining a reconstructed value of the first signal component samplingpoint of the current block according to the predicted value of the firstsignal component sampling point of the current block.

An embodiment of the present disclosure further provides a predictionapparatus for a signal component sampling point of an image block, whichincludes a first parameter unit configured to obtain a parameter of acorrelation model through calculation according to a reconstructed valueof a first adjacent signal component sampling point above a currentblock and a reconstructed value of a second adjacent signal componentsampling point above the current block; and a first predicting unitconfigured to calculate, based on the correlation model, a predictedvalue of a first signal component sampling point of the current blockaccording to a reconstructed value of a second signal component samplingpoint of the current block and the parameter of the correlation model.

An embodiment of the present disclosure further provides a predictionapparatus for a signal component sampling point of an image block, whichincludes a second parameter unit configured to obtain a parameter of acorrelation model through calculation according to a reconstructed valueof a first adjacent signal component sampling point on the left side ofa current block and a reconstructed value of a second adjacent signalcomponent sampling point on the left side of the current block; and asecond predicting unit configured to calculate, based on the correlationmodel, a predicted value of a first signal component sampling point ofthe current block according to a reconstructed value of a second signalcomponent sampling point of the current block and the parameter of thecorrelation model.

An embodiment of the present disclosure further provides an intra-framedecoding apparatus for a signal component sampling point of an imageblock, which includes a first obtaining unit configured to obtain, froma video code stream, prediction mode information of a first signalcomponent of a current block; a first determining unit configured todetermine a prediction mode of the first signal component of the currentblock from a prediction mode set of the first signal component of thecurrent block according to the prediction mode information of the firstsignal component of the current block, where the prediction mode set ofthe first signal component of the current block includes at least one ofan LMA mode and an LML mode; a third predicting unit configured toobtain a predicted value of a first signal component sampling point ofthe current block according to the prediction mode of the first signalcomponent of the current block; and a first calculating unit configuredto obtain a reconstructed value of the first signal component samplingpoint of the current block according to the predicted value of the firstsignal component sampling point of the current block.

An embodiment of the present disclosure further provides an intra-framedecoding apparatus for a signal component sampling point of an imageblock, which includes a second obtaining unit configured to obtain, froma video code stream, prediction mode information of a first signalcomponent of a current block; a second determining unit configured todetermine a prediction mode of the first signal component of the currentblock from a prediction mode set of the first signal component of thecurrent block according to the prediction mode information of the firstsignal component of the current block, where the prediction mode set ofthe first signal component includes a prediction mode based on acorrelation model, and the prediction mode based on the correlationmodel is determined depending on a prediction mode of a second signalcomponent of the current block; a fourth predicting unit configured toobtain a predicted value of a first signal component sampling point ofthe current block according to the prediction mode of the first signalcomponent of the current block; and a second calculating unit configuredto obtain a reconstructed value of the first signal component samplingpoint of the current block according to the predicted value of the firstsignal component sampling point of the current block.

According to the technical solutions provided in the embodiments of thepresent disclosure, by using a technical means of introducing an LMAmode and an LML mode in a process of intra-frame prediction of a currentblock, the accuracy of intra-frame prediction of the current block isimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solutions in the embodiments of the presentdisclosure more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments. Theaccompanying drawings in the following description show merely someembodiments of the present disclosure, and persons of ordinary skill inthe art may still derive other drawings from these accompanying drawingswithout creative efforts.

FIGS. 1A, 1B, and 1C are schematic diagrams of a luminance-chrominance(YUV) format;

FIG. 2 is a schematic diagram of an L-type template used for an LM mode;

FIGS. 3A and 3B are schematic diagrams showing distribution of samplingpoints in an L-type template and objects in a current block;

FIG. 4 is a schematic diagram of a template used for an LMA mode;

FIG. 5 is a schematic diagram of a template used for an LML mode;

FIG. 6 is a flowchart of an intra-frame decoding method for a signalcomponent sampling point of an image block according to an embodiment ofthe present disclosure;

FIG. 7 is a flowchart of an intra-frame decoding method for a signalcomponent sampling point of an image block according to anotherembodiment of the present disclosure;

FIG. 8 is an effect diagram of a V component of a reconstructed imageobtained using an embodiment of the present disclosure;

FIG. 9 is an effect diagram of a V component of a reconstructed imageobtained using the HEVC technical solution;

FIG. 10 is an effect diagram of a technical solution according to anembodiment of the present disclosure;

FIG. 11 is a schematic diagram of a prediction apparatus for a signalcomponent sampling point of an image block according to an embodiment ofthe present disclosure;

FIG. 12 is a schematic diagram of a prediction apparatus for a signalcomponent sampling point of an image block according to anotherembodiment of the present disclosure;

FIG. 13 is a schematic diagram of an intra-frame decoding apparatus fora signal component sampling point of an image block according to anembodiment of the present disclosure; and

FIG. 14 is a schematic diagram of an intra-frame decoding apparatus fora signal component sampling point of an image block according to anotherembodiment of the present disclosure.

DETAILED DESCRIPTION

The following clearly describes the technical solutions in theembodiments of the present disclosure with reference to the accompanyingdrawings in the embodiments of the present disclosure. The embodimentsto be described are merely a part rather than all of the embodiments ofthe present disclosure. All other embodiments obtained by persons ofordinary skill in the art based on the embodiments of the presentdisclosure without creative efforts shall fall within the protectionscope of the present disclosure.

A video image signal generally includes one luminance component and twochrominance components. The luminance component is generally indicatedby a symbol Y, and the chrominance components are generally indicated bysymbols U and V. As shown in FIGS. 1A, 1B, and 1C, common YUV formatsinclude the following formats, where a cross shown in FIGS. 1A, 1B, and1C indicates a luminance component sampling point, and a circleindicates each chrominance component sampling point: a 4:4:4 format:indicating that no downsampling is performed on a chrominance component;a 4:2:2 format: indicating that 2:1 horizontal downsampling is performedon a chrominance component relative to a luminance component, but novertical downsampling is performed, where for every two U samplingpoints or V sampling points, each scan line includes four Y samplingpoints; and a 4:2:0 format: indicating that 2:1 horizontal downsamplingand 2:1 vertical downsampling are performed on a chrominance componentrelative to a luminance component.

In a case where a video image uses a YUV4:2:0 format, if a luminancecomponent of an image block is an image block with a size of 2N×2N, achrominance component of the image block is an image block with a sizeof N×N. In the embodiments of the present disclosure, the technicalsolutions of the present disclosure are described using the 4:2:0 formatas an example. However, it may be understood that, in addition to theYUV4:2:0 format, the technical solutions of the present disclosure mayalso be applied to other YUV formats, or mutual prediction betweendifferent components in other video image formats, such as a red greenblue (RGB) format. In another aspect, a current block may be a squareblock, or may be a non-square rectangular block or an area in anothershape, to which the technical solutions provided in the embodiments ofthe present disclosure are also applicable.

For convenience of description, in the embodiments of the presentdisclosure, expressions such as a first signal component and a secondsignal component are used. If an image signal includes a luminancesignal component and a chrominance signal component, the first signalcomponent may be a chrominance component, and the second signalcomponent may be a luminance component; if the image signal includesthree signal components red (R), green (G), and blue (B), the firstsignal component may be any signal component in the three signalcomponents R, G, and B, and the second signal component may be a signalcomponent different from the first signal component in the three signalcomponents R, G, and B; and if the image signal is decomposed into aplurality of signal components in another manner, the first signalcomponent and the second signal component may be specified using asimilar method.

In the embodiments of the present disclosure, because two chrominancecomponents can be predicted from a luminance component using a samemethod, the technical solutions according to the embodiments of thepresent disclosure may be described in the following using L to indicatea luminance component and using C to indicate any one of chrominancecomponents. A predicted value of any chrominance component samplingpoint may be obtained by mapping a reconstructed value of a luminancecomponent sampling point at a same position according to a correlationfunction relation ƒ(x). When there is no luminance component samplingpoint at the same position corresponding to a chrominance componentsampling point (a position relation between a luminance componentsampling point and a chrominance component sampling point in the YUV4:2:0 format as shown in FIG. 1C), a luminance component may be firstre-sampled to a position of the chrominance component sampling point toobtain L′, and then prediction is performed, as shown in Formula (2.1).In this case, each chrominance component sampling point has oneluminance component value and one chrominance component value.Sample_(C) ^(pred)[j,i]=ƒ(Sample′_(L)[j,i])   (2.1)

Herein, the correlation function relationship ƒ(x) is used to express acorrelation model from a luminance component value to a chrominancecomponent value of a sampling point, and it may be a linear function, ormay be another function such as a quadratic polynomial. The embodimentsof the present disclosure are described using a linear function modelshown in Formula (2.2) as an example. Parameters α and β of the linearmodel may be obtained through calculation according to reconstructedvalues of a group of luminance component sampling points and chrominancecomponent sampling points.ƒ(x)=αx+β  (2.2)

The group of selected sampling points used for calculating theparameters α and β is called a template in the embodiments of thepresent disclosure. In the embodiments of the present disclosure, asshown in FIG. 2, an L-type template is used for an LM mode. The LM modeis a prediction mode for calculating a predicted value of a firstcomponent sampling point of a current block based on reconstructedvalues of first adjacent signal component sampling points above and onthe left side of the current block, reconstructed values of secondadjacent signal component sampling points above and on the left side ofthe current block, and a reconstructed value of a second componentsampling point of the current block.

The accuracy of the parameters α and β directly influences the accuracyof the predicted value of the chrominance component sampling point. TheL-type template used for the foregoing LM mode includes only N adjacentpoints right above the current block and N adjacent points on the leftside of the current block. Generally, the L-type template is effective.For example, an image block shown in FIG. 3A includes two objects, whichhave different chrominance components (a grey area and a white arearepresent two objects). However, in the L-type template, a plurality ofsampling points belongs to a same object as a part of sampling points inthe current block. In this case, correlation between a luminancecomponent and a chrominance component derived from the sampling pointsin the L-type template is quite similar to correlation betweencomponents in the current block. Therefore, a value of a chrominancecomponent sampling point in the current block can be accuratelypredicted, based on the foregoing linear relation, from a reconstructedvalue of a luminance component sampling point. However, if the twoobjects in the current block are distributed as shown in FIG. 3B (a greyarea and a white area represent two objects with different chrominancecomponents), that is, no sampling point in the L-type template belongsto a same object as a sampling point in the grey area, in this case, theparameters α and β obtained through calculation cannot indicatecorrelation between a luminance component and a chrominance component ofthe grey area. As a result, a value of a chrominance component samplingpoint of the grey area cannot be accurately predicted using a linearrelation derived in this case.

To accurately predict a value of a chrominance component sampling pointin a current block, the embodiments of the present disclosure providetwo new prediction modes, that is, an LMA mode and an LML mode.

As shown in FIG. 4, the LMA mode is a prediction mode for calculating apredicted value of a first component sampling point of a current blockbased on a reconstructed value of a first adjacent signal componentsampling point above the current block, a reconstructed value of asecond adjacent signal component sampling point above the current block,and a reconstructed value of a second component sampling point of thecurrent block.

In the embodiment of the present disclosure, the calculating thepredicted value of the first component sampling point of the currentblock based on the reconstructed value of the first adjacent signalcomponent sampling point above the current block, the reconstructedvalue of the second adjacent signal component sampling point above thecurrent block, and the reconstructed value of the second componentsampling point of the current block is only calculating the predictedvalue of the first component sampling point of the current block basedon the reconstructed value of the first adjacent signal componentsampling point above the current block, the reconstructed value of thesecond adjacent signal component sampling point above the current block,and the reconstructed value of the second component sampling point ofthe current block, that is, sampling points on the left side and on thelower left of the current block are not used in a process of calculatingthe predicted value of the first component sampling point of the currentblock.

As shown in FIG. 5, the LML mode is a prediction mode for calculating apredicted value of a first component sampling point of a current blockbased on a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block, a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block, and a reconstructed value of a secondcomponent sampling point of the current block.

In the embodiment of the present disclosure, the calculating thepredicted value of the first component sampling point of the currentblock based on the reconstructed value of the first adjacent signalcomponent sampling point on the left side of the current block, thereconstructed value of the second adjacent signal component samplingpoint on the left side of the current block, and the reconstructed valueof the second component sampling point of the current block is onlycalculating the predicted value of the first component sampling point ofthe current block based on the reconstructed value of the first adjacentsignal component sampling point on the left side of the current block,the reconstructed value of the second adjacent signal component samplingpoint on the left side of the current block, and the reconstructed valueof the second component sampling point of the current block, that is,sampling points right above and on the upper right of the current blockare not used in a process of calculating the predicted value of thefirst component sampling point of the current block.

In the following, with reference to FIG. 4, a prediction method for asignal component sampling point of an image block provided in anembodiment of the present disclosure is described as follows:calculating, based on a correlation model, a predicted value of a firstsignal component sampling point of a current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point above the current block and a reconstructed value of asecond adjacent signal component sampling point above the current block.

As described above, in the embodiment of the present disclosure, a firstsignal component may be a chrominance component, and a second signalcomponent may be a luminance component. In the following, thechrominance component and the luminance component are used as an examplefor description. In the embodiment of the present disclosure, thecorrelation model may be a linear model, or may be a quadraticpolynomial model or another correlation model.

In the embodiment of the present disclosure, the term “above” in “abovethe current block” may be right above, or upper left, or upper right, ora combination of right above, upper left and upper right.

It may be understood that, adjacent signal component sampling pointsabove the current block may be all adjacent sampling points above thecurrent block, or a part of adjacent sampling points above the currentblock, for example, a part of sampling points right above and a part ofsampling points on the upper left of the current block are selected.

In the embodiment of the present disclosure, a size of a chrominancecomponent image of the current block is nS, a value of an adjacentchrominance component sampling point above the current block isRec_(C)[x, y], a reconstructed value of a luminance component samplingpoint of the current block is Rec_(L)[x, y], and a reconstructed valueof an adjacent luminance component sampling point above the currentblock is Rec_(L)[x, y], where values of [x,y] in the two Rec_(L)[x, y]are different. Output of the embodiment of the present disclosure is apredicted value Pred_(C)[x, y] of a chrominance component samplingpoint.

The foregoing values of the sampling points are obtained throughreconstruction in a decoding operation before this process. Because apatent technology is described using a square block as an example in thepresent disclosure, that the size of the chrominance component image ofthe current block is nS indicates that the chrominance component imageof the current block includes nS×nS sampling points.

This procedure includes the following steps.

S401: Perform a re-sampling operation on a reconstructed value of aluminance component sampling point of a current block and areconstructed value of an adjacent luminance component sampling pointoutside the current block, to obtain a reconstructed value Rec′_(L)[x,y]of a luminance component sampling point at a position of a chrominancecomponent sampling point of the current block, where the reconstructedvalue Rec_(L)[x,y] is obtained after re-sampling, [x,y] indicatescoordinates of the chrominance component sampling point, and a samplingpoint in an upper left corner of the current block may be selected as anorigin of the coordinates. Definitely, if a reconstructed value of aluminance component sampling point exists at the position of thechrominance component sampling point of the current block, there-sampling operation is not required.

A re-sampling method is related to a sampling format of a video imagesignal. A purpose of re-sampling is to obtain a sampling value of aluminance component at the position of the chrominance componentsampling point of the current block. As shown in FIG. 4, for are-sampling manner used for the YUV4:2:0 format, a calculation method isas follows.Rec′_(L)[x,y]=(Rec_(L)[2x,2y]+Rec_(L)[2x,2y+1])>>1where (x, y) ε {(x, y)|x=0, . . . ,2*nS−1; y=−1}∪{(x, y)|x, y=0, . . .,nS−1}.   (2.3)

{(x, y)|x=0, . . . ,2*nS−1; y=−1} indicates an adjacent chrominancecomponent sampling point above the current block, {(x, y)|x, y=0, . . .,nS−1} indicates the chrominance component sampling point of the currentblock, and Rec′_(L)[x,y] indicates a luminance component sampling valueat the position of the chrominance component sampling point of thecurrent block, where the luminance component sampling value is obtainedafter re-sampling.

In addition to the foregoing re-sampling method, another re-samplingmethod may also be adopted.

The foregoing adjacent chrominance component sampling point {(x, y)|x=0,. . . ,2*nS−1; y=−1} above the current block forms a template for theLMA mode. Reconstructed values of luminance components and reconstructedvalues of chrominance components of all sampling points in the templateare used for calculating parameters α and β in a linear model.

S402: Calculate the parameters α and β in the linear model.

A linear regression technique is used to calculate the parameters α andβ in the linear model. Formulas (2.4) and (2.5) show an implementationmethod.

$\begin{matrix}{\alpha = \frac{{I*{LC}} - {C*L}}{{I*{LL}} - L^{2}}} & (2.4) \\{\beta = \frac{C - {\alpha*L}}{I}} & (2.5)\end{matrix}$

where I indicates the number of sampling points in the template, Lindicates a sum of reconstructed values of all luminance componentsampling points in the template, C indicates a sum of reconstructedvalues of all chrominance component sampling points in the template, LLindicates a quadratic sum of the reconstructed values of all theluminance component sampling points in the template, and LC indicates asum of products of the reconstructed values of all the luminancecomponent sampling points and the reconstructed values of all thechrominance component sampling points in the template. L, C, LL, and LCmay be obtained through calculation using Formulas (2.6), (2.7), (2.8),and (2.9).

$\begin{matrix}{L = {\sum\limits_{x = 0}^{{2*{nS}} - 1}{{Rec}_{L}^{\prime}\left\lbrack {x,{- 1}} \right\rbrack}}} & (2.6) \\{C = {\sum\limits_{x = 0}^{{2*{nS}} - 1}{{Rec}_{C}\left\lbrack {x,{- 1}} \right\rbrack}}} & (2.7) \\{{LL} = {\sum\limits_{x = 0}^{{2*{nS}} - 1}{{Rec}_{L}^{\prime}\left\lbrack {x,{- 1}} \right\rbrack}^{2}}} & (2.8) \\{{LC} = {\sum\limits_{x = 0}^{{2*{nS}} - 1}{{{Rec}_{L}^{\prime}\left\lbrack {x,{- 1}} \right\rbrack}*{{Rec}_{C}\left\lbrack {x,{- 1}} \right\rbrack}}}} & (2.9)\end{matrix}$

S403: Calculate a predicted value Pred_(C)[x,y] of the chrominancecomponent sampling point of the current block.

By substituting the parameters α and β obtained through calculation intothe linear model, the predicted value Pred_(C)[x, y] of the chrominancecomponent sampling point of the current block can be obtained throughcalculation based on the luminance component sampling value Rec′_(L)[x,y] at the position of the chrominance component sampling point of thecurrent block, where the luminance component sampling value Rec′_(L)[x,y] is obtained after re-sampling. An implementation manner is shown inFormula (2.10).Pred_(C)[x, y]=α*Rec′_(L)[x, y]+βwhere x,y=0, . . . ,nS−1.   (2.10)

In the following, with reference to FIG. 5, a prediction method for asignal component sampling point of an image block provided in anembodiment of the present disclosure is described as follows:calculating, based on a correlation model, a predicted value of a firstsignal component sampling point of a current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block and a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block.

As described above, in the embodiment of the present disclosure, a firstsignal component may be a chrominance component, and a second signalcomponent may be a luminance component. In the following, thechrominance component and the luminance component are used as an examplefor description. In the embodiment of the present disclosure, thecorrelation model may be a linear model, or may be a quadraticpolynomial model or another correlation model.

In the embodiment of the present disclosure, the term “left side” in “onthe left side of the current block” may be left, or upper left, or lowerleft, or a combination of left, upper left and lower left.

It may be understood that, adjacent signal component sampling points onthe left side of the current block may be all adjacent sampling pointson the left side of the current block, or a part of adjacent samplingpoints on the left side of the current block, for example, a part ofsampling points on the left of and a part of sampling points on theupper left of the current block are selected.

In the embodiment of the present disclosure, a size of a chrominancecomponent image of the current block is nS, a value of an adjacentchrominance component sampling point on the left side of the currentblock is Rec_(C)[x,y], a reconstructed value of a luminance componentsampling point of the current block is Rec_(L)[x, y], and areconstructed value of an adjacent luminance component sampling point onthe left side of the current block is Rec_(L)[x, y], where values of[x,y] in the two Rec_(L)[x, y] are different. Output of the embodimentof the present disclosure is a predicted value Pred_(C)[x, y] achrominance component sampling point.

The foregoing values of the sampling points are obtained throughreconstruction in a decoding operation before this process. Because apatent technology is described using a square block as an example in thepresent disclosure, that the size of the chrominance component image ofthe current block is nS indicates that the chrominance component imageof the current block includes nS×nS sampling points.

This procedure includes the following steps.

S501: Perform a re-sampling operation on a reconstructed value of aluminance component sampling point of a current block and areconstructed value of an adjacent luminance component sampling pointoutside the current block, to obtain a luminance component samplingvalue Rec′_(L)[x,y] value at a position of a chrominance componentsampling point of the current block, where the luminance componentsampling value Rec′_(L)[x,y] is obtained after re-sampling, [x,y]indicates coordinates of the chrominance component sampling point, and asampling point in an upper left corner of the current block may beselected as an origin of the coordinates. Definitely, if a reconstructedvalue of a luminance component sampling point exists at the position ofthe chrominance component sampling point of the current block, there-sampling operation is not required.

A re-sampling method is related to a sampling format of a video imagesignal. A purpose of re-sampling is to obtain a reconstructed value of aluminance component sampling point at the position of the chrominancecomponent sampling point of the current block. As shown in FIG. 5, for are-sampling manner used for the YUV4:2:0 format, a calculation method isas follows:Rec′_(L)[x,y]=(Rec_(L)[2x,2y]+Rec_(L)[2x,2y+1])>>1where (x, y) ε{(x, y)|x=−1; y=0, . . . ,2*nS−1}∪{(x, y)|x, y=0, . . .,nS−1}.   (2.11)

{(x, y)|x=−1; y=0, . . . ,2*nS−1} indicates an adjacent chrominancecomponent sampling point on the left side of the current block, {(x,y)|x, y=0, . . . ,nS−1} indicates the chrominance component samplingpoint of the current block, and Rec′_(L)[x,y] indicates the luminancecomponent sampling value at the position of the chrominance componentsampling point of the current block, where the luminance componentsampling value is obtained after re-sampling.

In addition to the foregoing re-sampling method, another re-samplingmethod may also be adopted.

The foregoing adjacent chrominance component sampling point {(x,y)|x=−1; y=0, . . . ,2*nS−1} on the left side of the current block formsa template for the LML mode. Reconstructed values of luminancecomponents and reconstructed values of chrominance components of allsampling points in the template are used for calculating parameters αand β in a linear model.

S502: Calculate the parameters α and β in the linear model.

A linear regression technique is used to calculate the parameters α andβ in the linear model. Formulas (2.4) and (2.5) show an implementationmethod.

$\begin{matrix}{\alpha = \frac{{I*{LC}} - {C*L}}{{I*{LL}} - L^{2}}} & (2.4) \\{\beta = \frac{C - {\alpha*L}}{I}} & (2.5)\end{matrix}$

where I indicates the number of sampling points in the template, Lindicates a sum of reconstructed values of all luminance componentsampling points in the template, C indicates a sum of reconstructedvalues of all chrominance component sampling points in the template, LLindicates a quadratic sum of the reconstructed values of all theluminance component sampling points in the template, and LC indicates asum of products of the reconstructed values of all the luminancecomponent sampling points and the reconstructed values of all thechrominance component sampling points in the template. L, C, LL, and LCmay be obtained through calculation using Formulas (2.12), (2.13),(2.14), and (2.15).

$\begin{matrix}{L = {\sum\limits_{y = 0}^{{2*{nS}} - 1}{{Rec}_{L}^{\prime}\left\lbrack {{- 1},y} \right\rbrack}}} & (2.12) \\{C = {\sum\limits_{y = 0}^{{2*{nS}} - 1}{{Rec}_{C}\left\lbrack {{- 1},y} \right\rbrack}}} & (2.13) \\{{LL} = {\sum\limits_{y = 0}^{{2*{nS}} - 1}{{Rec}_{L}^{\prime}\left\lbrack {{- 1},y} \right\rbrack}^{2}}} & (2.14) \\{{LC} = {\sum\limits_{y = 0}^{{2*{nS}} - 1}{{{Rec}_{L}^{\prime}\left\lbrack {{- 1},y} \right\rbrack}*{{Rec}_{C}\left\lbrack {{- 1},y} \right\rbrack}}}} & (2.15)\end{matrix}$

S503: Calculate a predicted value Pred_(C)[x,y] of the chrominancecomponent sampling point of the current block.

By substituting the parameters α and β obtained through calculation intothe linear model, the predicted value Pred_(C)[x, y] of the chrominancecomponent sampling point of the current block can be obtained throughcalculation based on the luminance component sampling value Rec′_(L)[x,y] at the position of the chrominance component sampling point of thecurrent block, where the luminance component sampling value Rec′_(L)[x,y] is obtained after re-sampling. An implementation manner is shown inFormula (2.10).Pred_(C)[x, y]=α*Rec′_(L)[x, y]+βwhere x,y=0, . . . ,nS−1.   (2.10)

In the following, with reference to FIG. 6, an intra-frame decodingmethod for a signal component sampling point of an image block providedin an embodiment of the present disclosure is described.

S601: Obtain, from a video code stream, prediction mode information of afirst signal component of a current block.

S602: Determine a prediction mode of the first signal component of thecurrent block from a prediction mode set of the first signal componentof the current block according to the prediction mode information of thefirst signal component of the current block, where the prediction modeset of the first signal component of the current block includes at leastone of an LMA mode and an LML mode.

As described above, in the embodiment of the present disclosure, thefirst signal component may be a chrominance component, and a secondsignal component may be a luminance component. In the following, thechrominance component and the luminance component are used as an examplefor description.

In the embodiment of the present disclosure, the chrominance componentof the current block may have its own independent chrominance predictionmode, or may share a same chrominance prediction mode with a chrominancecomponent of an adjacent image block. For example, in an existing HEVCencoding and decoding solution, each predicting unit has an independentprediction mode, and one predicting unit may include one or moretransform units. In an encoding and decoding process of a chrominancecomponent, a prediction operation is performed for the current blockbased on the transform unit. If one predicting unit includes only onetransform unit, the transform unit has its own independent predictionmode; and if one predicting unit includes a plurality of transformunits, the plurality of transform units uses a same prediction mode.

A decoding end may adopt an adaptive arithmetic entropy decoding method,variable length decoding, fixed length decoding or another entropydecoding method to obtain, from a code stream, prediction modeinformation of a chrominance component, where the prediction modeinformation is expressed by a code word, and then determine a predictionmode of a chrominance component of a current predicting unit accordingto correspondence between a code word and a prediction mode, so as todetermine a prediction mode of a chrominance component of a transformunit in the predicting unit, that is, the current block. Specifically,which entropy decoding method to be adopted depends on a code worddesigning method of an intra-frame prediction mode for chrominance. Acode table shown in Table 1 shows correspondence between an availablecode word and a prediction mode of a chrominance component.

TABLE 1 Code table of a prediction mode of a chrominance componentPrediction Mode of Code Word Chrominance Component 0 DM mode 101 LM mode1001 LMA mode 1000 LML mode 110 Planar mode 1110 Vertical mode 11110Horizontal mode 11111 DC mode

A code word of an original prediction mode of the chrominance componentin the HEVC solution is a Truncated Unary (TU) code. In this embodiment,a code word 10 of the LM mode is extended, and in addition, suffix codewords 1, 01, and 10 are added to distinguish the LM mode, a newly addedLMA mode, and an LML mode, so as to obtain the code table shown inTable 1. Obviously, other code words may also be selected for the LMAmode and the LML mode to form a new code table. In addition, a single TUcode, a Huffman code, a fixed length code or another code word, or acombined code word with different code words may also be adopted tospecify a corresponding code word for all prediction modes of thechrominance component, so as to form a new code table.

For the code table shown in Table 1, it may be considered that theprediction mode set of the first signal component of the current blockincludes: the DM mode, the LM mode, the LMA mode, the LML mode, theplanar mode, the vertical mode, the horizontal mode, and the DC mode.

S603: Obtain a predicted value of a first signal component samplingpoint of the current block according to the prediction mode of the firstsignal component of the current block.

In the embodiment of the present disclosure, if the prediction mode ofthe first signal component of the current block that is determined fromthe prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block is the LMA mode, the obtaining apredicted value of a first signal component sampling point of thecurrent block according to the prediction mode of the first signalcomponent of the current block includes calculating, based on acorrelation model, the predicted value of the first signal componentsampling point of the current block according to a reconstructed valueof a second signal component sampling point of the current block and aparameter of the correlation model, where the parameter of thecorrelation model is obtained through calculation according to areconstructed value of a first adjacent signal component sampling pointabove the current block and a reconstructed value of a second adjacentsignal component sampling point above the current block.

If the prediction mode of the first signal component of the currentblock that is determined from the prediction mode set of the firstsignal component of the current block according to the prediction modeinformation of the first signal component of the current block is theLML mode, the obtaining a predicted value of a first signal componentsampling point of the current block according to the prediction mode ofthe first signal component of the current block includes calculating,based on a correlation model, the predicted value of the first signalcomponent sampling point of the current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block and a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block.

A specific prediction method has been described in detail in theembodiments shown in FIG. 4 and FIG. 5, and is not described hereinagain.

S604: Obtain a reconstructed value of the first signal componentsampling point of the current block according to the predicted value ofthe first signal component sampling point of the current block.

A reconstructed value of a chrominance component sampling point of thecurrent block is calculated based on an obtained predicted value of thechrominance component sampling point of the current block and a residualvalue of the chrominance component sampling point of the current block,where the residual value is obtained through reconstruction. Theresidual value of the chrominance component sampling point of thecurrent block may be obtained based on residual information of thechrominance component sampling point of the current block, where theresidual information is obtained from a video code stream. The H.264/AVCstandard or a method in the existing HEVC solution may be adopted toreconstruct the residual value of the chrominance component samplingpoint of the current block, which is not described herein again.

In some implementation manners, another code table may be adopted inS602, and a code table shown in Table 2 shows correspondence between anavailable code word and a prediction mode of a chrominance component.

TABLE 2 Code table of a prediction mode of a chrominance componentPrediction Mode of Code Word Chrominance Component 0 DM mode 10 LM mode110 LMA mode 111 LML mode

Code words of original six prediction modes of the chrominance componentin the HEVC solution are TU codes. In this embodiment, four existingHEVC prediction modes are removed, and TU codes are used to design codewords for the LMA, LML and other remaining modes. Obviously, the codetable may also be redesigned by removing one or more other existing HEVCprediction modes, or adding a new suitable prediction mode. A new codetable may adopt a single TU code, a Huffman code, a fixed length code oranother code word, or a combined code word with different code words tospecify a corresponding code word for all optional prediction modes ofthe chrominance component.

For the code table shown in Table 1, it may be considered that theprediction mode set of the first signal component of the current blockincludes the DM mode, the LM mode, the LMA mode, and the LML mode.

According to the technical solution provided in the embodiment of thepresent disclosure, by using a technical means of providing a predictionmode set including an LMA mode and an LML mode for a chrominancecomponent, the accuracy of intra-frame prediction of a current block isimproved.

In the following, with reference to FIG. 7, an intra-frame decodingmethod for a signal component sampling point of an image block providedin an embodiment of the present disclosure is described.

S701: Obtain, from a video code stream, prediction mode information of afirst signal component of a current block.

S702: Determine a prediction mode of the first signal component of thecurrent block from a prediction mode set of the first signal componentof the current block according to the prediction mode information of thefirst signal component of the current block, where the prediction modeset of the first signal component includes a prediction mode based on acorrelation model, and the prediction mode based on the correlationmodel is determined depending on a prediction mode of a second signalcomponent of the current block.

In the embodiment of the present disclosure, the prediction mode basedon the correlation model includes a prediction mode for calculating apredicted value of a first signal component sampling point of thecurrent block using the correlation model according to a reconstructedvalue of a second signal component sampling point of the current blockand a parameter of the correlation model; and the prediction mode basedon the correlation model may include any one of the following predictionmodes an LM mode, an LMA mode, and an LML mode.

In the embodiment of the present disclosure, a parameter of thecorrelation model of the LMA mode is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point above the current block and a reconstructed value of asecond adjacent signal component sampling point above the current block;a parameter of the correlation model of the LML mode is obtained throughcalculation according to a reconstructed value of a first adjacentsignal component sampling point on the left side of the current blockand a reconstructed value of a second adjacent signal component samplingpoint on the left side of the current block; and a parameter of thecorrelation model of the LM mode is obtained through calculationaccording to the reconstructed values of the first adjacent signalcomponent sampling points above and on the left side of the currentblock and the reconstructed values of the second adjacent signalcomponent sampling points above and on the left side of the currentblock.

As described above, in the embodiment of the present disclosure, thefirst signal component may be a chrominance component, and the secondsignal component may be a luminance component. In the following, thechrominance component and the luminance component are used as an examplefor description.

In the embodiment of the present disclosure, the chrominance componentof the current block may have its own independent chrominance predictionmode, or may share a same chrominance prediction mode with a chrominancecomponent of an adjacent image block. For example, in an existing HEVCencoding and decoding solution, each predicting unit has an independentprediction mode, and one predicting unit may include one or moretransform units. In a frame encoding and decoding process of achrominance component, a prediction operation is performed for thecurrent block based on the transform unit. If one predicting unitincludes only one transform unit, the transform unit has its ownindependent prediction mode; and if one predicting unit includes aplurality of transform units, the plurality of transform units uses asame prediction mode.

A decoding end may adopt an adaptive arithmetic entropy decoding method,variable length decoding, fixed length decoding or another entropydecoding method to obtain, from a code stream, prediction modeinformation of a chrominance component, where the prediction modeinformation is expressed by a code word, and then determine a predictionmode of a chrominance component of a current predicting unit accordingto correspondence between a code word and a prediction mode, so as todetermine a prediction mode of a chrominance component of a transformunit in the predicting unit, that is, the current block. Specifically,which entropy decoding method to be adopted depends on a code worddesigning method of an intra-frame prediction mode for chrominance. Acode table shown in Table 3 shows correspondence between an availablecode word and a prediction mode of a chrominance component.

TABLE 3 Code table of a prediction mode of a chrominance componentPrediction Mode of Code Word Chrominance Component 0 DM mode 101 Firstmode 100 Second mode 110 Planar mode 1110 Vertical mode 11110 Horizontalmode 11111 DC mode

In the embodiment of the present disclosure, the first mode or thesecond mode is a prediction mode based on a correlation model, and maybe one of the LM mode, the LML mode, and the LMA mode. When it isdetermined that the prediction mode of the chrominance component is thefirst mode or the second mode, a prediction mode indicated by the firstmode or the second mode needs to be obtained based on a preset mappingtable according to a prediction mode of a luminance component of thecurrent block. The foregoing mapping table is used at both an encodingend and a decoding end. For example, the prediction modes indicated bythe first mode and the second mode may be determined based on a mappingshown in Table 4 according to the prediction mode of the luminancecomponent. Obviously, the mapping has a plurality of combinations, andis not limited to Table 4.

TABLE 4 Mapping between the prediction mode of the luminance componentand the first mode and the second mode Intra-frame Prediction Mode forLuminance First Mode Second Mode Vertical mode LM mode LMA modeHorizontal mode LM mode LML mode DC mode LM mode LML mode Anotherintra-frame LML mode LMA mode prediction mode

A code word of an original prediction mode of the chrominance componentin the HEVC solution is a TU code. In this embodiment, a code word 10 ofthe LM mode is extended, and in addition, suffix code words 1 and 0 areadded to distinguish the first mode from the second mode, so as toobtain the code table shown in Table 3. Obviously, other code words maybe selected for the first mode and the second mode to form a new codetable, and a single TU code, a Huffman code, a fixed length code oranother code word, or a combined code word with different code words mayalso be adopted to specify a corresponding code word for all optionalprediction modes of the chrominance component, so as to form a new codetable.

For convenience of understanding, in the embodiment of the presentdisclosure, possible methods of determining the prediction mode of thechrominance component of the current block are briefly described usingexamples. For example, in some implementation manners, if it isdetermined, according to the prediction mode information of thechrominance component, that the prediction mode of the chrominancecomponent of the current block is a prediction mode based on acorrelation model, that is, the first mode or the second mode shown inTable 3, the prediction mode of the chrominance component of the currentblock is determined based on Table 4 according to the prediction mode ofthe luminance component of the current block. For another example, insome implementation manners, the first mode and the second mode shown inTable 3 may also be determined based on Table 4 according to theprediction mode of the luminance component of the current block, and inthis case, the prediction mode of the chrominance component of thecurrent block may be determined directly according to the predictionmode information of the chrominance component.

For the code table shown in Table 3, it may be considered that theprediction mode set of the first signal component of the current blockincludes at least one prediction mode of the DM mode, the planar mode,the vertical mode, the horizontal mode, the DC mode, and the predictionmode based on the correlation model.

S703: Obtain a predicted value of a first signal component samplingpoint of the current block according to the prediction mode of the firstsignal component of the current block.

In the embodiment of the present disclosure, if the prediction mode ofthe first signal component of the current block that is determined fromthe prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block is the LMA mode, the obtaining apredicted value of a first signal component sampling point of thecurrent block according to the prediction mode of the first signalcomponent of the current block includes calculating, based on thecorrelation model, the predicted value of the first signal componentsampling point of the current block according to the reconstructed valueof the second signal component sampling point of the current block andthe parameter of the correlation model, where the parameter of thecorrelation model is obtained through calculation according to thereconstructed value of the first adjacent signal component samplingpoint above the current block and the reconstructed value of the secondadjacent signal component sampling point above the current block.

If the prediction mode of the first signal component of the currentblock that is determined from the prediction mode set of the firstsignal component of the current block according to the prediction modeinformation of the first signal component of the current block is theLML mode, the obtaining a predicted value of a first signal componentsampling point of the current block according to the prediction mode ofthe first signal component of the current block includes calculating,based on the correlation model, the predicted value of the first signalcomponent sampling point of the current block according to thereconstructed value of the second signal component sampling point of thecurrent block and the parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to the reconstructed value of the first adjacent signalcomponent sampling point on the left side of the current block and thereconstructed value of the second adjacent signal component samplingpoint on the left side of the current block.

A specific prediction method has been described in detail in theembodiments shown in FIG. 4 and FIG. 5, and is not described hereinagain.

S704: Obtain a reconstructed value of the first signal componentsampling point of the current block according to the predicted value ofthe first signal component sampling point of the current block.

A reconstructed value of a chrominance component sampling point of thecurrent block is calculated based on an obtained predicted value of thechrominance component sampling point of the current block and a residualvalue of the chrominance component sampling point of the current block,where the residual value is obtained through reconstruction. Theresidual value of the chrominance component sampling point of thecurrent block may be obtained based on residual information of thechrominance component sampling point of the current block, where theresidual information is obtained from a video code stream. The H.264/AVCstandard or a method in the existing HEVC solution may be adopted toreconstruct the residual value of the chrominance component samplingpoint of the current block, which is not described herein again.

In some implementation manners, another code table may be adopted inS702, and a code table shown in Table 5 shows correspondence between anavailable code word and a prediction mode of a chrominance component.

TABLE 5 Code table of a prediction mode of a chrominance componentPrediction Mode of Code Word Chrominance Component 0 DM mode 10 Firstmode 110 Planar mode 1110 Vertical mode 11110 Horizontal mode 11111 DCmode

In the embodiment of the present disclosure, the first mode is aprediction mode based on a correlation model, and may be one of the LMmode, the LML mode, and the LMA mode. When it is determined that theprediction mode of the chrominance component is the first mode, aprediction mode indicated by the first mode needs to be determined basedon a preset mapping table according to a prediction mode of a luminancecomponent of the current predicting unit. The foregoing mapping table isused at both an encoding end and a decoding end. Table 6 shows a mappingbetween an available prediction mode of the luminance component and thefirst mode. Obviously, the mapping has a plurality of combinations, andis not limited to Table 6.

TABLE 6 Mapping between the prediction mode of the luminance componentand the first mode Prediction Mode of Luminance Component First ModeVertical mode LMA mode Horizontal mode LML mode DC mode LML mode Anotherintra-frame LM mode prediction mode

A code word of an original prediction mode of the chrominance componentin the HEVC solution is a TU code. In this embodiment, code words of allthe optional prediction modes of the chrominance component still use TUcodes. Obviously, a single Huffman code, a fixed length code or anothercode word, or a combined code word with different code words may also beadopted to specify a corresponding code word for all the optionalprediction modes of chrominance component, so as to form a new codetable.

For convenience of understanding, in the embodiment of the presentdisclosure, possible methods of determining the prediction mode arebriefly described using examples. For example, in some implementationmanners, if it is determined, according to the prediction modeinformation of the chrominance component, that the prediction mode ofthe chrominance component of the current block is a prediction modebased on a correlation model, that is, the first mode shown in Table 5,the prediction mode of the chrominance component of the current block isdetermined based on Table 6 according to the prediction mode of theluminance component of the current block. For another example, in someimplementation manners, the first mode shown in Table 5 may bedetermined based on Table 6 according to the prediction mode of theluminance component of the current block, and in this case, theprediction mode of the chrominance component of the current block may bedetermined directly according to the prediction mode information of thechrominance component.

For the code table shown in Table 5, it may be considered that theprediction mode set of the first signal component of the current blockincludes at least one prediction mode of the DM mode, the planar mode,the vertical mode, the horizontal mode, the DC mode, and the predictionmode based on the correlation model.

According to the technical solution provided in the embodiment of thepresent disclosure, by using a technical means of providing a predictionmode set including an LMA mode and an LML mode for a chrominancecomponent, the accuracy of intra-frame prediction of a current block isimproved.

With the technical solution provided in the embodiment of the presentdisclosure, the accuracy of intra-frame prediction of a current block isimproved, and beneficial effects of the embodiment of the presentdisclosure are described in detail from the following two aspects.

The first aspect is a subjective aspect. FIG. 8 shows a V component of areconstructed image obtained using the solution in the embodiment of thepresent disclosure, and FIG. 9 shows a V component of a reconstructedimage obtained using an existing HEVC solution (that is, predictionmodes of a chrominance component include only a DM mode, an LM mode, ahorizontal mode, a vertical mode, a planar mode, and a DC mode). It canbe seen by comparing FIG. 8 and FIG. 9 that the reconstructed imageshown in FIG. 8 is sharper, and has clearer details. This is because twooptional prediction modes of the chrominance component that are newlyadded in the embodiment of the present disclosure enable intra-frameprediction of the chrominance component to be more accurate, so that aprediction residual is smaller. Accordingly, distortion caused byquantization of the prediction residual is not obvious, therebyobtaining a better reconstructed image.

In the second aspect, comparison that uses a method for objectivelyevaluating Blue-ray Disc Bitrate (BD-Bitrate) shows that the embodimentof the present disclosure has better rate distortion performance.Specific data is shown in Table 7. Values shown in Table 7 indicate apercentage of a bit rate saved by the embodiment of the presentdisclosure, compared with the existing HEVC solution. If the percentageis negative, the bit rate is saved; and if the percentage is positive,the bit rate is increased.

TABLE 7 All Intra HE All Intra LC Y U V Y U V Class A −0.2% −9.1% −9.9%−0.1% −9.3% −10.1% Class B −0.1% −2.7% −2.2% 0.0% −2.8% −2.2% Class C−0.2% −2.3% −2.9% −0.1% −2.2% −2.7% Class D −0.1% −2.0% −2.2% −0.1%−2.0% −2.2% Class E −0.1% −1.5% −1.8% 0.0% −1.9% −1.8% Class F −0.3%−2.6% −2.9% −0.2% −2.2% −2.6% Overall −0.2% −3.4% −3.6% −0.1% −3.4%−3.6% −0.2% −3.4% −3.6% −0.1% −3.4% −3.5% Enc Time [%] 105% 107% DecTime [%] 100% 100%

FIG. 10 is a rate-distortion diagram showing comparison of results ofencoding a sequence SteamLocomotive using the embodiment of the presentdisclosure and the existing HEVC solution HEVC Test Model (HM) 4.0. Itcan be seen that, with the method provided in the present disclosure,encoding performance is definitely enhanced, and subjective quality isimproved.

As shown in FIG. 11, an embodiment of the present disclosure provides aprediction apparatus for a signal component sampling point of an imageblock, which includes a first parameter unit 1101 configured to obtain aparameter of a correlation model through calculation according to areconstructed value of a first adjacent signal component sampling pointabove a current block and a reconstructed value of a second adjacentsignal component sampling point above the current block; and a firstpredicting unit 1102 configured to calculate, based on the correlationmodel, a predicted value of a first signal component sampling point ofthe current block according to a reconstructed value of a second signalcomponent sampling point of the current block and the parameter of thecorrelation model.

The apparatus provided in the embodiment of the present disclosure isconfigured to implement the method shown in FIG. 4, which is notdescribed herein again.

As shown in FIG. 12, an embodiment of the present disclosure provides aprediction apparatus for a signal component sampling point of an imageblock, which includes a second parameter unit 1201 configured to obtaina parameter of a correlation model through calculation according to areconstructed value of a first adjacent signal component sampling pointon the left side of a current block and a reconstructed value of asecond adjacent signal component sampling point on the left side of thecurrent block; and a second predicting unit 1202 configured tocalculate, based on the correlation model, a predicted value of a firstsignal component sampling point of the current block according to areconstructed value of a second signal component sampling point of thecurrent block and the parameter of the correlation model.

The apparatus provided in the embodiment of the present disclosure isconfigured to implement the method shown in FIG. 5, which is notdescribed herein again.

As shown in FIG. 13, an embodiment of the present disclosure provides anintra-frame decoding apparatus for a signal component sampling point ofan image block, which includes a first obtaining unit 1301 configured toobtain, from a video code stream, prediction mode information of a firstsignal component of a current block; a first determining unit 1302configured to determine a prediction mode of the first signal componentof the current block from a prediction mode set of the first signalcomponent of the current block according to the prediction modeinformation of the first signal component of the current block, wherethe prediction mode set of the first signal component of the currentblock includes at least one of an LMA mode and an LML mode; a thirdpredicting unit 1303 configured to obtain a predicted value of a firstsignal component sampling point of the current block according to theprediction mode of the first signal component of the current block; anda first calculating unit 1304 configured to obtain a reconstructed valueof the first signal component sampling point of the current blockaccording to the predicted value of the first signal component samplingpoint of the current block.

The apparatus provided in the embodiment of the present disclosure isconfigured to implement the method shown in FIG. 6, which is notdescribed herein again.

According to the apparatus provided in the embodiment of the presentdisclosure, by using a technical means of providing a prediction modeset including an LMA mode and an LML mode for a chrominance component,the accuracy of intra-frame prediction of a current block is improved.

As shown in FIG. 14, an embodiment of the present disclosure provides anintra-frame decoding apparatus for a signal component sampling point ofan image block, which includes a second obtaining unit 1401 configuredto obtain, from a video code stream, prediction mode information of afirst signal component of a current block; a second determining unit1402 configured to determine a prediction mode of the first signalcomponent of the current block from a prediction mode set of the firstsignal component of the current block according to the prediction modeinformation of the first signal component of the current block, wherethe prediction mode set of the first signal component includes aprediction mode based on a correlation model, and the prediction modebased on the correlation model is determined depending on a predictionmode of a second signal component of the current block; a fourthpredicting unit 1403 configured to obtain a predicted value of a firstsignal component sampling point of the current block according to theprediction mode of the first signal component of the current block; anda second calculating unit 1404 configured to obtain a reconstructedvalue of the first signal component sampling point of the current blockaccording to the predicted value of the first signal component samplingpoint of the current block.

The apparatus provided in the embodiment of the present disclosure isconfigured to implement the method shown in FIG. 7, which is notdescribed herein again.

According to the apparatus provided in the embodiment of the presentdisclosure, by using a technical means of providing a prediction modeset including an LMA mode and an LML mode for a chrominance component,the accuracy of intra-frame prediction of a current block is improved.

The technology provided in the embodiments of the present disclosure maybe applied to the field of digital signal processing and may beimplemented using an encoder and a decoder. A video encoder and decoderare widely applied to various communications devices or electronicdevices, such as a digital television, a set top box, a media gateway, amobile phone, a wireless apparatus, a personal digital assistant (PDA),a handheld or portable computer, a global positioning system (GPS)receiver/navigator, a camera, a video player, a video camera, a videotape recorder, a monitoring device, and a video conference and avideophone device. Such a device includes a processor, a memory, and aninterface for data transmission. A video codec may be directlyimplemented by a digital circuit or a chip, such as a digital signalprocessor (DSP), or may be implemented by software code driving aprocessor to execute a procedure in the software code.

Persons of ordinary skill in the art may understand that all or a partof the steps of the foregoing method embodiments of the presentdisclosure may be implemented by a program instructing relevanthardware. The foregoing program may be stored in a computer readablestorage medium. When the program is run, the steps of the foregoingmethod embodiments are performed. The foregoing storage medium includesany medium that is capable of storing program code, such as a read-onlymemory (ROM), a random-access memory (RAM), a magnetic disk, or anoptical disc.

Finally, it should be noted that the foregoing embodiments are merelyintended for describing the technical solutions of the presentdisclosure rather than limiting the present disclosure. Although thepresent disclosure is described in detail with reference to theforegoing embodiments, persons of ordinary skill in the art shouldunderstand that they may still make modifications to the technicalsolutions described in the foregoing embodiments or make equivalentreplacements to some technical features thereof, as long as suchmodifications or replacements do not make the essence of correspondingtechnical solutions depart from the spirit and scope of the technicalsolutions in the embodiments of the present disclosure.

What is claimed is:
 1. An intra-frame decoding method for a signalcomponent sampling point of an image block, comprising: obtaining, froma video code stream, prediction mode information of a first signalcomponent of a current block; determining a prediction mode of the firstsignal component of the current block from a prediction mode set of thefirst signal component of the current block according to the predictionmode information of the first signal component of the current block,wherein the prediction mode set of the first signal component of thecurrent block comprises at least one of a linear model above (LMA) modeand a linear model left (LML) mode, wherein the LMA mode is a predictionmode for calculating a predicted value of a first component samplingpoint of the current block based on the reconstructed value of the firstadjacent signal component sampling point above the current block, thereconstructed value of the second adjacent signal component samplingpoint above the current block, and a reconstructed value of a secondcomponent sampling point of the current block, and wherein the LML modeis a prediction mode for calculating the predicted value of the firstcomponent sampling point of the current block based on the reconstructedvalue of the first adjacent signal component sampling point on the leftside of the current block, the reconstructed value of the secondadjacent signal component sampling point on the left side of the currentblock, and the reconstructed value of the second component samplingpoint of the current block; obtaining a predicted value of a firstsignal component sampling point of the current block according to theprediction mode of the first signal component of the current block; andobtaining a reconstructed value of the first signal component samplingpoint of the current block according to the predicted value of the firstsignal component sampling point of the current block.
 2. The methodaccording to claim 1, wherein when the prediction mode of the firstsignal component of the current block that is determined from theprediction mode set of the first signal component of the current blockaccording to the prediction mode information of the first signalcomponent of the current block is the. LMA mode, obtaining the predictedvalue of the first signal component sampling point of the current blockaccording to the prediction mode of the first signal component of thecurrent block comprises calculating, based on a correlation model, thepredicted value of the first signal component sampling point of thecurrent block according to a reconstructed value of a second signalcomponent sampling point of the current block and a parameter of thecorrelation model, wherein the parameter of the correlation model isobtained through calculation according to a reconstructed value of afirst adjacent signal component sampling point above the current blockand a reconstructed value of a second adjacent signal component samplingpoint above the current block.
 3. The method according to claim 1,wherein when the prediction mode of the first signal component of thecurrent block that is determined from the prediction mode set of thefirst signal component of the current block according to the predictionmode information of the first signal component of the current block isthe LML mode, obtaining the predicted value of the first signalcomponent sampling point of the current block according to theprediction mode of the first signal component of the current blockcomprises calculating, based on a correlation model, the predicted valueof the first signal component sampling point of the current blockaccording to a reconstructed value of a second signal component samplingpoint of the current block and a parameter of the correlation model,wherein the parameter of the correlation model is obtained throughcalculation according to a reconstructed value of a first adjacentsignal component sampling point on the left side of the current blockand a reconstructed value of a second adjacent signal component samplingpoint on the left side of the current block.
 4. The method according toclaim 1, wherein the prediction mode set of the first signal componentof the current block comprises a direct mode (DM) mode, a linear method(LM) mode, the LMA mode, the LML mode, a planar mode, a vertical mode, ahorizontal mode, and a DC mode.
 5. The method according to claim 1,wherein the prediction mode set of the first signal component of thecurrent block comprises a direct mode (DM) mode, a linear method (LM)mode, the LMA mode, and the LML mode.
 6. The method according to claim1, wherein the LM mode is a prediction mode for calculating thepredicted value of the first component sampling point of the currentblock based on the reconstructed values of the first adjacent signalcomponent sampling points above and on the left side of the currentblock, the reconstructed values of the second adjacent signal componentsampling points above and on the left side of the current block, and thereconstructed value of the second component sampling point of thecurrent block.
 7. The method according to claim 1, wherein the firstsignal component is a chrominance component, and wherein a second signalcomponent is a luminance component.
 8. An intra-frame decoding methodfor a signal component sampling point of an image block, comprising:obtaining, from a video code stream, prediction mode information of afirst signal component of a current block; determining a prediction modeof the first signal component of the current block from a predictionmode set of the first signal component of the current block according tothe prediction mode information of the first signal component of thecurrent block, wherein the prediction mode set of the first signalcomponent comprises a prediction mode based on a correlation model, andthe prediction mode based on the correlation model is determineddepending on a prediction mode of a second signal component of thecurrent block; obtaining a predicted value of a first signal componentsampling point of the current block according to the prediction mode ofthe first signal component of the current block; and obtaining areconstructed value of the first signal component sampling point of thecurrent block according to the predicted value of the first signalcomponent sampling point of the current block, wherein the predictionmode based on the correlation model is a prediction mode for calculatingthe predicted value of the first signal component sampling point of thecurrent block using the correlation model according to a reconstructedvalue of a second signal component sampling point of the current blockand a parameter of the correlation model, wherein the prediction modebased on the correlation model is any one of the following predictionmodes a linear model above (LMA) mode and a linear model left (LML)mode, wherein the LMA mode is a prediction mode for calculating apredicted value of a first component sampling point of the current blockbased on the reconstructed value of the first adjacent signal componentsampling point above the current block, the reconstructed value of thesecond adjacent signal component sampling point above the current block,and a reconstructed value of a second component sampling point of thecurrent block, and wherein the LML mode is a prediction mode forcalculating the predicted value of the first component sampling point ofthe current block based on the reconstructed value of the first adjacentsignal component sampling point on the left side of the current block,the reconstructed value of the second adjacent signal component samplingpoint on the left side of the current block, and the reconstructed valueof the second component sampling point of the current block.
 9. Themethod according to claim 8, wherein a parameter of the correlationmodel of the LMA mode is obtained through calculation according to areconstructed value of a first adjacent signal component sampling pointabove the current block and a reconstructed value of a second adjacentsignal component sampling point above the current block, wherein aparameter of the correlation model of the LML: mode is obtained throughcalculation according to a reconstructed value of a first adjacentsignal component sampling point on the left side of the current blockand a reconstructed value of a second adjacent signal component samplingpoint on the left side of the current block, and wherein a parameter ofthe correlation model of the LM mode is obtained through calculationaccording to the reconstructed values of the first adjacent signalcomponent sampling points above and on the left side of the currentblock and the reconstructed values of the second adjacent signalcomponent sampling points above and on the left side of the currentblock.
 10. The method according to claim 8, wherein when the predictionmode of the first signal component of the current block that isdetermined from the prediction mode set of the first signal component ofthe current block according to the prediction mode information of thefirst signal component of the current block is the LMA mode, obtainingthe predicted value of the first signal component sampling point of thecurrent block according to the prediction mode of the first signalcomponent of the current block comprises calculating, based on thecorrelation model, the predicted value of the first signal componentsampling point of the current block according to the reconstructed valueof the second signal component sampling point of the current block andthe parameter of the correlation model, wherein the parameter of thecorrelation model is obtained through calculation according to thereconstructed value of the first adjacent signal component samplingpoint above the current block and the reconstructed value of the secondadjacent signal component sampling point above the current block. 11.The method according to claim 8, wherein when the prediction mode of thefirst signal component of the current block that is determined from theprediction mode set of the first signal component of the current blockaccording to the prediction mode information of the first signalcomponent of the current block is the mode, obtaining the predictedvalue of the first signal component sampling point of the current blockaccording to the prediction mode of the first signal component of thecurrent block comprises calculating, based on the correlation model, thepredicted value of the first signal component sampling point of thecurrent block according to the reconstructed value of the second signalcomponent sampling point of the current block and the parameter of thecorrelation model, wherein the parameter of the correlation model isobtained through calculation according to the reconstructed value of thefirst adjacent signal component sampling point on the left side of thecurrent block and the reconstructed value of the second adjacent signalcomponent sampling point on the left side of the current block.
 12. Themethod according to claim 8, wherein the prediction mode set of thefirst signal component of the current block comprises at least oneprediction mode of a direct mode (DM) mode, a planar mode, a verticalmode, a horizontal mode, a direct current (DC) mode, and the predictionmode based on the correlation model.
 13. The method according to claim8, wherein the first signal component is a chrominance component, andwherein the second signal component is a luminance component.
 14. Aprediction method for a signal component sampling point of an imageblock, comprising: calculating, based on a correlation model, apredicted value of a first signal component sampling point of a currentblock according to a reconstructed value of a second signal componentsampling point of the current block and a parameter of the correlationmodel, wherein the parameter of the correlation model is obtainedthrough calculation according to a reconstructed value of a firstadjacent signal component sampling point in a reference block and areconstructed value of a second adjacent signal component sampling pointin the reference block, and wherein the reference block comprises one orany combination of the following blocks: an upper left block of thecurrent block, an upper right block of the current block, and rightabove block of the current block.
 15. The method according to claim 14,wherein a first signal component is a chrominance component, and whereinthe second signal component is a luminance component.
 16. A predictionmethod for a signal component sampling point of an image block,comprising: calculating, based on a correlation model, a predicted valueof a first signal component sampling point of a current block accordingto a reconstructed value of a second signal component sampling point ofthe current block and a parameter of the correlation model, wherein theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point in a reference block and a reconstructed value of asecond adjacent signal component sampling point in the reference block,and wherein the reference block comprises one or any combination of thefollowing blocks: an upper left block of the current block, a lower leftblock of the current block, and left block of the current block.
 17. Themethod according to claim 16, wherein a first signal component is achrominance component, and wherein the second signal component is aluminance component.